Why Do We Have Summer?

Summer starts on the longest day of the year. We call that day the summer solstice.
Summer days are warm and long. There is more sunlight. People spend more time outdoors.
Why do we have summer? Earth tilts as it travels around the sun. When Earth’s northern half leans toward the sun, that part has summer.
Summer starts in the northern half of Earth around June 21. At that time, it is winter in the southern part of Earth. That is because the Earth’s southern half is tilted away from the sun.